text: Proforms of NGF and BDNF (proNGF and proBDNF) are precursors to NGF and BDNF. proNGF and proBDNF interact with p75NTR and cause p75NTR-mediated apoptosis without activating TrkA-mediated survival mechanisms. Cleavage of proforms into mature Neurotrophins allows the mature NGF and BDNF to activate TrkA-mediated survival mechanisms.